Hornbills are large distinctive tropical birds, found only in the African and Asian continents. These are the only birds that have a two-lobed kidney and the only ones in which the first two vertebrae (the axis and atlas) are fused together. There are 54 species of hornbills in the world out of which 13 of them have been recorded from Thailand alone. Hornbills play some important ecological roles such as dispersal of seeds from the fruits they eat and control of some prey species. Some scientists are also using Hornbills as an ecological indicator to indicate good condition of the forest as the forest bares enough food and contains big trees; trees that Hornbills use for breeding must be very large with large diameter so that females and chicks can stay inside the cavity with ease.

Habitat: Rainforests are the major habitats for Asian hornbills. Some species are found in deciduous forest such as great hornbills and oriental pie hornbills.

Feed: Hornbills are primarily fruit eating birds. They eat various species of fig (Ficus sp.) More than 60 species of non-fig fruits are consumed by them. However, some of them like Brown hornbills even eat some small animals such as mouse, lizards, snakes, geckos and some insects for protein and calcium source.

Breeding: Hornbill's breeding season starts late rainy season from October to May. Hornbills use the cavity in the tree for building their nests. The nest sizes are measured up to their body size. The Breeding behavior of the Hornbills is very attractive for wilderness enthusiast for these birds pair for years and sometimes, for their entire life. When the male meets an attractive female, he tries to spoil her with valuable feed such as; prey animals or juicy fruits. Females then test her mate-to-be by trashing those gifts away. The Male will try again and again to show his ability and will also prepare appropriate surrounding conditions for the females to lay eggs. When female accepts that male, he will further lure her to the nesting site by precious feed. She then, observes the nest cavity and if she is satisfied, she will allow that male to copulate several times in a day. While she is going in and out and starts to seal the opening with mud, food and faeces, the male keeps bringing her the precious feed and copulates too. Female will lay several eggs and incubate them till the hatching day. Large species sometime burst the seal to help the males feed their chick's. Females of smaller species will stay inside the nest hole and go out the same time when the chicks fledge.

Status: The major limiting factors for the decline in the number of hornbills are the decrease in the number of their and not enough nest cavities. Many of the rainforests are being used as human settlements and agricultural areas; the minor reasons being hunting and poaching. Now, IUCN status of this species is critically endangered. CITES categorized these species into appendix 1.

The main idea of this study is to intervene with the limiting factor and make them offering factors. The major target is to obtain more successful breeding while learning. "How" and "Why" the birds choose their nest hole. The results of this study can be used as a recommendation for nest box construction which can lead to more promising outcomes. Scientists who work on "Artificial nest box programme" for wild hornbills can also use information gained from this study to design artificial nest boxes.

The authors wish to contribute this information to enhance captive breeding which will assist conservation of these critically endangered species both in wild and captive conditions.

Objectives

1. The nest box selection plays an important role in Hornbill's captive breeding which will reflect the success of the captive breeding programs. We therefore need to know "how" the process of nest box selection done and "why" do hornbills select those particular nest boxes only.

2. The controlled factors of research were run under proven conditions of successful breeding, both in the natural and captive condition. The conditions were; nutrients requirement, thickness and dimension of holes' opening, minimum space requirement, nest hole-filling substances, height of the floor to hole opening .The hornbills in this project already showed paired behavior.

3. Variance factors for the nest boxes are space or dimension, shape, materials and height installing sites. These factors and the interactive behavior can determine reasons for selection; preferences of more space, firmness of nest boxes, fluctuation of temperature, security, imprinted shapes of previous use as chicks and preference of low temperature. 4. Aim is to use the results from this study to enhance recommendations of nest box production and installing to the management.

5. The results of this study can also help artificial nest box programs for the wild hornbills in the required area, as some areas are already facing the limitation of nest boxes and affected number of success breeding pairs.

Results

General

1. From two seasons of the study (2000 - 2001), we obtained 10 chicks; comprising of 9 Oriental Pied Hornbills and 1 Greater Hornbill.

2. The success birth rate is 50% i.e., 7 out of 14 pairing attempts. The 7 successful cases comprised of 2 pairs from the first year and 5 pairs from the second year. The 2 pairs, which were successes from the first year, still proved to be successful in the second year.

Installing sites

1. In conclusion, the success of birth rates was found in pairs that selected nest boxes that were installed at the higher sites.

3.Notice from the study: The species that used box-shaped boxes were the Greater Hornbills and Wreath Hornbills, which are considered as large species. Dimension may contribute to this action.

Sex and the observation

1. From 16 boxes observed, 50 % was observed from both sexes and 50 % was solely from female.

2. All 8 boxes that were observed from both sexes, males were in advance to observe in every case. But most of the observations from males were protruding of the head into nest opening while females were going into the boxes.

3. In conclusion, all the successful boxes, females are the nest box selector. Nevertheless males remained observers .But whenever males protruded heads into the boxes, females would also follow with his observation.

Materials

1. From 7 successful cases at chick obtaining rate; Pile wood box was used 1 box (as 14.29%), concrete pipes were used 3 times (as 42.87%), metal barrels were used 3 times (as 42.87%) and wooden stripes boxes were not used at all.

2. From 16 successful cases at going-in rate; Pile wood boxes were observed 25.00 %, concrete pipes were observed 18.75%, metal barrels were observed 18.75% and wooden stripe boxes were 37.50%.

3. From 206 successful at observed rate, Pile wood boxes were observed 70.39 %, concrete pipes were observed 1.46%, metal barrels were observed 9.22% and wooden stripe boxes were 18.39%.

Pile wood boxes were the most attractive to observe, but the most successful nest boxes were concrete pipes and metal barrels.

Temperature

1. Different temperatures (lower) from ambient are different in each material. The most different were wooden boxes. Pile wood boxes, concrete pipes and metal barrels were lower in difference, consecutively.

2. Fluctuation of temperature in day-time was least in wooden stripe boxes. Pile wood boxes, concrete pipes and metal barrels were lower consecutively.

Conclusion and discussion

Controlled Factors

Relationship between hornbills: Every pair of hornbills was observed to be paired already at the least rate of staying close together. This factor was found to be crucial for this study. Some pairs that showed no sign of paring behavior was excluded from the study. The paring behavior is studied in other research categories, undertake by the same authors.

Hornbill body condition: We were able to measure the health of the hornbills through physically examining each individual to determine the weight and muscle consistency around the keel. This was done by using the Body Condition Index (David, 1945) in which we palpate the breast muscles and sternum (keel). The degree of development or energy storage of skeletal muscles can be estimated. The body condition index is graded on a scale of one to five, with one being very thin and five being well-muscled or plump. All the hornbills measured were found to be not less than two on this scale.

Age: We were able to estimate the age of the hornbills by the size of the casque and the color of the iris. All birds in this study were adult.

Diet: Oriental Pied Hornbill: Food is offered once daily, comprised of banana cubes, papaya cubes and grapes, with commercial dry dog feed. For Great Hornbill; food is offered once daily, a similar diet to that of the Oriental Pied Hornbill but offered with the addition of milled rice with boiled eggs ( mainly for sealing purpose ). These additional items are rolled into 1-2 cm. diameter balls. Supplements to the diet include seashells finely ground for calcium supplement which is sprinkled on the food every day. Two types of the following items were added daily as compliment; guava cubes, orange pieces, boiled pumpkin cubes, boiled carrot cubes, fichus fruits, black plum fruits, pinky mice, and pieces of pork meat, small lizards and geckos. The amount of individual items remaining in the food tray must be weighed every day. If one type of food is completely consumed, we increased that item to try and determine which food item was preferred. At an average number, feed composition (from feed intake study) comprise of proteins at 12.18%, fat 3.73%, calcium 0.71% and phosphorus 0.49%.

Cage: Size of enclosure used in study is 4m wide by 8m long by 3m tall.

Nest Site: We used a total of 8 nest boxes with 4 set approximately 2 meters high and 4 set 30cm off the ground. Boxes were made from pile wood, metal barrels, concrete pipe, or wooden stripe assembling together in cylindrical shape and seal with cement.

Height of nest opening: Access to the nest boxes was 7-10cm from the bottom of the box.

Opening dimension: Larger hornbills such as; Great Hornbills and Rhinoceros Hornbill entry size was approximately 15cm. in width and not less than 20cm in height. Smaller Hornbills such as the Oriental Pied Hornbills, entry size was 10cm wide and not less than 16cm high. Elliptical or oval shape openings can be used but irregular shape with high streak opening is more suitable as the hornbills can seal this shape more effectively.

Nesting debris: Materials added to all nest boxes includes; soil, wood shavings, decayed wood from local forest. This material is added to a depth of 5cm high inside nest box. Some birds would then remove materials on their own from within the boxes. Materials utilized by hornbills to seal the cavity include a mixture of nesting material, food and fecal material. In 2001, a plywood nest box was chosen by the Great Hornbill; however the seal was not maintained properly due to the hornbill's addition of bananas to the mixture. This food choice did not dry adequately and acted not suitable as a sealing material. In 2002, the same pair of birds used milled rice with boiled egg yolk resulting in a successful seal.

Variable factors

Installing sites: The higher found to be better.

Shape and dimension: In small hornbills, pile wood boxes that had more space to the other shapes were observed more frequently but the hornbills chose concrete pipes and metal barrels without choosing any pile wood boxes. Contra to large hornbill species, wooden stripe boxes were more frequently observed but not accepted. The successful pair chose pile wood boxes which was the most space offering. Construction of wooden stripe may have flaws, as we cannot seal the wooden stripe to the point that no small hole presented.

Temperature: The best materials to keep temperature most lowly to ambient and least fluctuate were wooden stripe boxes. The wooden boxes were observed the most but none were selected at chick obtaining rate. This was against hypothesis that suggests temperature keeping is one of the most preferable factors as in the wild. In the wild, the birds prefer live tree than dead tree.

Materials: Concrete pipes and metal barrels were most used in successful cases; pile wood box was following in the success rate. While Concrete pipes and metal barrels were prominent in durability and security, but gave no good condition for temperature keeping, lower in space and dimension. We think that in captive condition that gave fair change of temperature, security is more preferable than space.

Suggestions for Nest box Management

1. For small species, metal barrels or concrete pipes were the most recommended. Installation must be as high as possible. Metal barrel has advantage of light-weight and easy to install.

2. For large species, pile wood boxes were most recommended. Install at high site, give more space and modify opening as close to nature as possible.